This invention is related to improved methods and compositions to enhance stain resistance of carpet fibers. Sulfonated aromatic condensates alone in a new process or in combination with other compounds are used to improve stain resistance. Related technology is disclosed in commonly assigned, copending applications Ser. No. 889,705 filed Jul. 28, 1986, on sulfonated benzotriazoles and Ser. No. 074,487 filed Jul. 23, 1987, on sulfonated aromatic formaldehyde condensates, such as diphenyl ether condensates.
The following terms are defined for use in this specification.
By sulfonated aromatic condensate (s.a.c.) is meant any condensate of an aromatic compound whether sulfonated prior to or after condensation, particularly sulfonated aromatic formaldehyde condensate (s.a.f.c.), effective to enhance stain resistance of fiber or carpet fabric.
By thiocyanate is meant any salt, organic or inorganic, containing a cation and the thiocyanate anion.
By fluorocarbon is meant those fluorocarbon compounds effective to improve the antisoiling properties of fiber or carpet fabric.
By ICP is meant index of crystalline perfection, a measured indication of the internal crystal structure of the polymer in an oriented fiber. High ICP indicates an open crystalline internal structure, easily dyeable polymer fiber.
By nylon is meant the polyamide family of polymers, nylon 6, nylon 6,6, nylon 4, nylon 12 and the other polymers containing the ##STR1## structure along with the --CH.sub.2 --.sub.x chain.
By carpet fabric is meant carpet fiber or yarn which has been typically tufted, woven, or otherwise constructed into fabric suitable for final use in home furnishings, particularly as floor covering.
By fiber is meant continuous filament of a running or extremely long length or cut or otherwise short fiber known as staple. Carpet yarn may be made of multiple continuous filaments or spun staple fiber, both typically pretextured for increased bulk.
By salt having a divalent cation is meant any such salt effective to enhance stain resistance of fiber, particularly high ICP nylon fiber, when combined with an effective amount of a s.a.c.
By dispersing agent is meant any chemical compound or combination of chemical compounds effective to make stable, relatively nonprecipitating, noncoagulating mixtures of other chemical compounds.
By sequestering agent is meant any chelating agent which is effective in sequestration, which is the suppression of certain properties of a metal without removing it from the system or phase. To be practical, the sequestering agent must not cause any undesirable change that would render the system unsuitable for its intended purpose. Chelation produces sequestration mainly by reducing the concentration of free metal ion to a very low value by converting most of the metal to a soluble chelate that does not possess the properties to be suppressed.
A chelating agent is a compound containing donor atoms that can combine by coordinate bonding with a single metal atom to form a cyclic structure called a chelation complex or, simply, a chelate. Because the donor atoms are connected intramolecularly by chains of other atoms, a chelate ring is formed for each donor atom after the first which coordinates with the metal. The above is from Volume 5, beginning page 339, of the Kirk-Othmer Encyclopedia of Chemical Technology (John Wiley & Sons), 1979, hereby incorporated by reference to p. 367.
It is known to use sulfonated aromatic formaldehyde condensates ("s.a.f.c."s) in the yarn finish (during or after fiber quenching) to improve stain resistance of carpet fiber, see U.S. Pat. No. 4,680,212, in the dye bath for the same purpose, see U.S. Pat. No. 4,501,591 or incorporated into the fiber for the same purpose, see U.S. Pat. No. 4,579,762. All three above U.S. patents are hereby incorporated by reference, in toto. Use of fluorochemical to improve both stain and soil resistance in combination with s.a.f.c.'s is also taught in U.S. Pat. No. 4,680,212, column 5. Other useful fluorochemicals for antisoiling are taught in commonly assigned U.S. Pat. Nos. 4,192,754; 4,209,610; 4,414,277; 4,604,316; 4,605,587 all also hereby incorporated by reference, in toto.
It is known to use thiocyanates, such as ammonium thiocyanate, at different process conditions as "assists" during dyeing for various purposes. See U.S. Pat. Nos. 3,652,199; 3,576,588; 3,387,913; 2,899,262; and 2,615,718 all hereby incorporated by reference, in toto.
Use of salts containing a divalent cation, such as magnesium sulfate, with s.a.f.c.'s to improve wet fastness is known in U.S. Pat. No. 3,790,344, hereby incorporated by reference, in toto. Also see page 48 of a textbook by Rosen, M. J., Surfactants & Interficial Phenomena (Wiley, 1978).
It is also known generally to use acid, including citric acid to buffer a dye bath and to use dispersing agents and/or sequestering agents to stabilize a aqueous formulations of chemicals.
Nylon carpets may be permanently discolored or stained by certain artificial colorants, such as food dyes, or oxidizing agents, such as acne preparations containing benzoyl peroxide. S.A.C.'s, applied to the fiber to provide an ionic barrier to food colorants, make the fiber more stain resistant, but are not effective against oxidizing agents. Furthermore, many of the s.a.c.'s used commercially for the preparation of "stain resistant" carpets are themselves, susceptible to oxidation upon exposure to light and ozone. This results in a yellowing of the s.a.c. and subsequent destruction. This has a major impact on the carpet properties. The yellow color of the s.a.c. results in a perceptible shift in the color of the carpet. Destruction of the s.a.c. results in a loss of the stain resistance properties of the carpet.
Use of fluorocarbon compound treated nylon fiber in carpet fabric inhibits wetting of the fiber surfaces which also inhibits any staining agent from being adsorbed onto or absorbed into the fiber. This surface wetting inhibition can be insufficient when the staining agent is dropped on the carpet with enough force to break the surface energy of the fluorocarbon surface barrier or not cleaned from the carpet and left in contact with fibers for extended time. Carpet treated with compositions containing s.a.c.'s must not interfere with the antisoiling properties of the fluorocarbon.
Application of s.a.c. to the carpet fabric must be effective, economical, and compatible to both untreated and fluorocarbon treated fiber, and to both continuous dyeing and Beck or batch dyeing. The same is true of any s.a.c. application formulation. The s.a.c. formulation must achieve effective penetration into the carpet fabric. Exhaustion of the individual active chemical components of any s.a.c. formulation must also be effective if not complete.
Certain nylon polymer fibers have very open internal crystal structure, namely high ICP polymer fiber, which require large amounts of s.a.c. to impart an effective degree of stain resistance. High ICP polymers are usually the result of high temperature saturated steam heat setting processes.
Some prior compositions and methods are only marginally acceptable regarding durability of the stain resistance when the carpet is steam cleaned with a detergent at a high pH.